Logistics Reduction: Heat Melt Compactor (LR-HMC)

The Advanced Exploration Systems (AES) Logistics Reduction (LR) project Heat Melt Compactor (HMC) technology is a waste management technology. Currently, there are no waste management practices that are being implemented in the space environment other than manual compaction of waste into a plastic bag. The current practice does not recover critical resources such as water, does not prevent the growth of potentially harmful microbiological pathogens, and provides only limited volume reduction.

The primary purpose of the HMC is to reduce the volume and microbiologically stabilize the waste. The HMC is a device that compacts and heats the trash. The trash is heated to the point where some of the plastic softens and fills the interstitial voids between non-melted trash. The compacted trash is then cooled, resulting in a dry, relatively solid tile that does not exhibit the spring back of traditional compactors. The shape of the tile is predictable and maximizes the efficiency of storage volume. When the trash is heated, it results in a microbiologically-safe tile that can be safely handled by the crew. The HMC can process both wet and dry trash. The water that is driven off the waste is collected and returned to the Water Recovery System. The tiles have ~10% hydrogen by mass from the plastics, wipes, and residual food and can be used to provide additional radiation shielding in the spacecraft.

A full-scale, second-generation (Gen2) HMC has been developed and is being used to finalize operational parameters and identify hardware issues. Gen2 HMC tests will allow development of an eventual ISS flight unit. Several SBIR awards related to HMC have occurred in the following areas: microgravity-compatible condensing heat exchanger designs, trash bag liners to allow hygienic tiles after HMC processing, and general HMC system design.

Limited Gen2 HMC ground testing began in 2017 but was not completed due to inability to reach desired compaction pressure and vacuum.  In FY18, the hardware was repaired to partially restore its desired capability.  In FY19, two contractors were selected for Phase A contracts under the NASA Next Space Technologies for Exploration Partnerships (NextSTEP) Appendix F: Logistics Reduction (LR) in Space by Trash Compaction and Processing System (TCPS) Broad Agency Announcement (BAA): Sierra Nevada Corporation (SNC) and UTC Aerospace Systems (UTAS, also known as Collins Aerospace) (https://www.nasa.gov/feature/nasa-selects-two-companies-to-help-take-out-the-deep-space-trash/ ), which will be completed in FY20.  This work includes a PDR and testing of ground prototype units, that will inform the FY21 Phase B TCPS NextSTEP procurement.  This phase of the project includes development of a TCPS flight unit for ISS, with delivery and on-orbit demonstration planned for ~2023.

In FY20, the ARC team continues risk reduction activities that include tests of the HMC Gen2 under different operational scenarios to inform TCPS contractors as they develop their PDR designs and prototypes.  Additionally, the Gen2 HMC will be used to test a MSFC catalytic oxidizer and an ARC design adsorption water recovery system. Semi-permeable trash containment bags from Materials Modification, Inc. (MMI) will be tested for their ability to reduce gas and water contaminants while allowing water recovery.